Drafting t-square



APil 27, 1937- R. H.V CUTTING 2,078,601

DRAFTING T-SQUARE Filed 0G12. 25, 1935 MMXW INVENTOR. Ricbam f7. Cuff/7J?.

ATTORNEY.

Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to geometric instruments and particularly to T squares and the like employed in drafting and for similar purposes.

It is one of the objects of this invention to provide a drafting instrument of the T square type comprising a straight edge stem portion and a head, having improved means for adjustably positioning the straight edge portion at an angle to the head.

Another object is to provide, in a drafting instrument of the T square type, an improved construction of head adapted to be moved along the edge of a drafting board or the like.

A Another object is to provide, in a drafting instrument of the T square type, an improved construction of straight edge stem portion of the T square.

Another object is to provide, in a T square of the pivoted head type, improved means for pivotally securing the head to the stem or straight edge portion.

Another object is to provide a drafting instrument of the T square typehaving improved crosssectional form in the headand stem or straight edge portion whereby they operate in an improved manner, in use.

Another object is to; provide-a drafting instrument orV the like of the T Ysquare type, the head and the stem or straight edge portion of which may be constructed from extruded metal.

Other objects will beapparent to those skilled in the art to which my invention appertains.

My invention is fully disclosed in the following description taken in connection with the accompanying drawing, in which:

Fig. l is a perspective view illustrating an embodiment of my invention associated with a drafting board;

Fig. 2 is a sectional view taken from the plane 2--2 of Fig. 1;

Fig. 3 is a view taken from the plane 3-3, vdrawn to a larger scale and with parts broken away for clearness;

Fig. 4 is a sectional view taken from the plane 4-4 of Fig. 1;

Fig. 5 is a fragmentary view to a larger scale illustrating a part of Fig. 4 and showing a mode of operation thereof;

Fig. 6 is a view showing separately an element of the embodiment oi Fig. 1;

Fig. '7 is a view similar to a part of Fig. 4, drawn to a larger scale and illustrating a modification;

Fig. 8 is a view similar to Fig. 7 illustrating still another modification;

(Cl. 33e-99) Fig. 9 is a fragmentary view illustrating a further modlfication and use of my invention.

Referring to the drawing, I have shown generally at I a drawing board having a sheet of drawing paper 26 thereon, retained thereon by thumb tacks 3-3. 'Ihe T square illustrating an embodiment of my invention is shown generally at 4 and comprises a stem or straight edge portion 5 and a head portion 6. Although as will be apparent, as the following description of my invention proceeds, the stem 5 and head` 6 may be made from various materials and by'various fabricating processes, I prefer to form these elements from extruded metal, and have illustrated such a T square.

The head B comprises an intermediate web portion 'I having along one side of the web a longitudinal bead 8 provided on its upper side with a flat face 9. At the other side of the web I is a flange I provided on its upper side with a flat face II. The two faces 9 and II above described are preferably elevated above the web 'I and are in a common plane. The ange I0 has a guiding surface I2 at right angles to the plane oi the said faces and adapted to slide along the edge of the drafting board I. Between the guiding surface I2 and the face I I, the flange I 0 isvprovided with relief I3 in the form of rectangular beads.

The stem or straight edge portion of the T square is generally of I section comprising an u intermediate web I 4 and longitudinally extending fiange portions I5-I5 at the opposite sides of the web. The anges I5 preferably have vertical end faces IG-IB and large radius bead-form edges I'I-I'I, the bead-form edges I'I preferably all being alike and symmetrically disposed with respect to the web I4.

'I'he head 6 is provided with a perforation I8 in the web 1 thereof substantially mid-way between its ends, and the web I4 has a perforation I9 adjacent one end thereof and mid-Way between its edges. To assemble the head with the straight edge portion, a bolt is projected through the aligned perforations I8 and I9, the head 2| of the bolt engaging by its under side the web 'I of the head; and a nut, preferably a wing nut I22 threaded on the bolt engaging the web I4. The head is preferably provided with pairs of aligned recesses 22 and 23 in the faces respectively II and 9 of the head and in these recesses the rounded edges I'I-II of the straight edge portion of the T square are disposed. The two parts of the T square 5 and 6 are thus interlocked together when the wing nut I22 is drawn up tight on the bolt 20 and the recesses 22-23 being dis- Cir posed in a line at right angles to the face I2 oi the head, the straight edge portion 5, or the faces II-IG at the edges thereof are thereby disposed accurately at a right angle to the face I2.

A complete T square is thus provided having ruling edges I--IG for guiding a ruling pen 24 or for suitably positioning and guiding triangles or the like. Furthermore, the straight edge portion 5 may be disposed at any desired angle with the head 6, one position being indicated at in broken lines in Fig. 1. This may be accomplished simply by loosening the nut |22 until the edges I1 of the portion 5 can be withdrawn from the recesses 22--23 and then the portion 5 may be rotated to the desired angular position and fixed in that position by tightening the wing nutk |22.v

`As shown in Fig. 5, one nib of a ruling pen may be guided by the face I5 even if held in a vertical position and at the same time, the rounded edge I1 where it contacts the paper 26, will be spaced relatively remotely from the points of the pen 21 contacting the paper so that there is no danger that ink will run under the edge of the T square.

If preferred, to hold the pen 24 in an inclined position as illustrated in Fig. 4, the rounded edge I1 in conjunction with the face I6 will suitably guide the pen. y

By providing the T square portion 5 of I section, the web I4 thereof will have clearance with the heads of thumb tacks such as that shown at 3 under the web I4, and the T square will not rock on the head as is the case with prior T squares. When the T square is moved up and down upon the drawing board, the rounded edges of the T square will readily ride up over thumb tacks as shown in solid line in Fig. 4 at 3 without mutilating the edge, or loosening the tacks.

The straight edge portion 5, being of symmetrical crossfsection, may be turned over,` or upsidedown, if for any reason the edges thereof should become mutilated or worn or nicked to render them unsuitable to guide the ruling pen, thus providing a fresh edge for that purpose which greatly increases the durability and life of the instrument.

As will readily be apparent also, the two parts of the T squarey may be separated upon loosening the wing nut |22 so that the instrument may be packed for transportation in the minimum of space.

If it be desired to provide the ruling edges of the stem portion 5 of the T square with transparent ruling strip in accord with the practice of some prior T squares, this may be done as illustrated in Fig. 7, one or both of the opposite edges of the Stem portion 5 of the T square being formed with a dovetail groove 28, and a strip of Celluloid or like transparent material 29 lmay be provided having a dovetail tongue 30 fitting the groove 28, the strip 29 having a suitable ruling edge 3 I.

In this connection it will be noted that the strip 3| clears the paper 26 by a space 32 which prevents the under side of the strip 3| from rubbing on the paper and becoming abraded in use and rendering it less clearly transparent.

The straight edge portion 5 of the T square may be completely removed from the head 5 by means of the wing nut |22 and bolt 2D, and may be used simply as a straight edge for drafting Work generally.

While I prefer to embody my invention as above described in strips of extruded metal, in some casesl it may be desired to make the two parts 5 and 6 out of wood or other similar material. In Fig. 8 is illustrated in cross-section 8f Stem portion f portions I4 and 1,

5a of the T square formed from wood and provided at its opposite edges with strips of celluloid or like transparent material 33-33 having grooves 34 therein into which the edges of the strip 5m are inserted and secured. With this construction, the recesses 22-23 above described in the head 5, will be shaped to conform to the strip 33.

As stated above, the straight edge portion 5 may be detached from the head portion 6 and used separately. This possibility leads to a number of advantages, among which are that a single head 6 may be provided for a number of straight edge portions 5 of different lengths constituting a set. The ordinary length may be used for ordinary work and the long length used for extraordinarily large work and one detached and the other put on the head by means of the wing nut |22, as will be understood, thus obviating the necessity of purchasing T squares of different lengths.

. Also, a straight edge portion 5 having the crosssection above described may be used without the head 6 in ways well understood in the drafting practice; and in this connection furthermore, the structure of the straight edge portion 5 adapts it admirably to use as a parallel-movement straight edge of well known mode of operation comprising grooved pulleys on the corners of the drafting board and flexible cords running thereon connected at opposite ends to a straight edge element. When the straight edge portion is to be used in this manner, it may be made as illustrated in Fig. 9 at 5bi,.such straight edge element having the cross-section hereinbefore described and illustrated in Figs. 1, 3 and 4, and additionally, adjacent the opposite ends thereof may be provided with oblong perforations 35-35, which perforations may be of the size and shape conventionally used with parallel-moving straight edgesl of the type above referred to.

When it is desired to make the web I4 of the straight edge portion 5 and the body 1 of the head E relatively thin, it may be preferred to employ therebetween at the screw 20, a rubber or other compressible washer 36, Fig. 2, upon which the compression applied by the wing nut |22 may be received to avoid undue distortion of the said If preferred, the web I4 of the straight edge portion 5 may be perforated to enable the user to see the drawing thereunder. Such perforations may be so formed as to render the web I4 of lattice formation as shown in Fig. 1 where the perforations 31-31 provide this effect. Wet ink lines can therefore be seen through and under the straight edge portion and the work maybe viewed through the perforations to facilitate positioning the straight edge portion.

The upper surface of the straight edge portion 5 is, as above described, channel form and pencils may be laid thereon without rolling off even at a considerable angle from thev horizontal of the board; and printed or other formulae or like data may be provided onthe web I4 and will not be rubbed olf inasmuch as it will lie in a channel and will be preserved even if the straight edge portion be turned upsidedown as above provided for. I My invention is not limited to the exact details of construction illustrated and described. Many changes and modifications may be. made therein without departing from the spirit of my invention or sacrificing its advantages and Within the scope of the appended claims.

I claim:

1. In a drafting T square, an elongated head having a pair of spaced longitudinally extending elevated beads on the upper side thereof and a longitudinally extending depending ange for engagement with the drawing board edge, a stem portion comprising a main body in the form of an elongated web and depending bead portions at opposite edges thereof adapted to rest upon a drawing board and support the body above the board and to guide a ruling pen, the elevated beads of the head having recesses therein for receiving the beads of the stem portion at an end portion thereof, means pivotally connecting the stem portion to the head and for clamping the stem portion to the head in a plurality of relatively rotated positions and in one position predetermined by the engagement of the said beads with the said recesses.

2. In a drafting T square, a head, a ruling edge portion secured thereto comprising a main body in the form of a longitudinally extending web and spaced longitudinally extending beads there on adapted to guide a ruling pen and adapted to rest upon a drafting board to support the body above the board, the head having longitudinally extending upstanding edge portions abutting the beads of the ruling portion whereby the intermediate body portions of the ruling edge portion and head are maintained in spaced relation, clamping means projected through said body portions, and resilient means interposed between the body portions whereby the clamping means will maintain the head in a plurality of rotated positions relative to the ruling edge portion.

3. A drafting T square comprising a guiding head of I section providing thickened longitudinally extending edge portions and a relatively thin intermediate body portion, one of said edge portions being adapted to guidingly abut a drawing board edge, a ruling stem portion of I section adapted to be supported on a drawing board by the I anges and maintain the intermediate body portions spaced from the drawing board, the guiding head and stem portions being disposed in overlapping relation and engaging only at the flanges to maintain the respective body portions in spaced relation, and clamping means projected through said body portions adapted to secure the head in a plurality of rotated positions relative to the ruling stem portion.

4. In a drafting T square, a head comprising a body in the form of an elongated web having generally parallel elevated bead portions extending longitudinally along opposite edges of the web and a depending flange along one longitudinal edge adapted to abut a drawing board edge, the bead portions having spaced pairs of aligned recesses therein, and a ruling edge portion secured to the head having corresponding bead portions for engagement with the recesses in the head to predeterminedly position the ruling edge portion on the head.

RICHARD H. CUTTING. 

